TWI751945B - An electrolyte and its application - Google Patents

Abstract

The invention discloses an electrolyte. The electrolyte comprises a salt and a silicone. The salt comprises lithium salt, sodium salt, potassium salt or their combination and is 10~50 weight percentage based on total weight of the electrolyte. The silicone has a structure as shown in formula (1).

Description

An electrolyte and its application

The present invention discloses an electrolyte and its application. Specifically, the electrolyte is a solid electrolyte with polar end groups made of a cross-linked epoxy/siloxane prepolymer. Its main application is in the field of battery technology, especially as an electrolyte for lithium batteries to prevent the destruction of lithium dendrites.

The specific capacity of the battery using the conventional electrolyte is only 50 mAh/g at 70 degrees Celsius, and the specific capacity retention rate of multiple charge/discharge cannot be achieved. On the other hand, the network structure film is prepared by reaction as the substrate of colloidal electrolyte (GPE), although this kind of film has the characteristics of flame resistance. However, the content of the colloidal electrolyte contains a certain amount of solvent, which causes the battery to have safety problems and the disadvantages of difficult to control the uniformity of each thin film in the manufacturing process.

To sum up, in the field of battery-related industries, an electrolyte with both optimized material properties and excellent electrical properties is an urgent issue to be developed.

Based on the aforementioned technical background, the basis of the present invention is mainly to use the reaction method of epoxy group/amine group to prepare the electrolyte of the specifications required by the lithium battery, and then add a compound of high polarity terminal group according to different requirements to achieve the purpose of modification. The highly polar end-group compounds do not affect the electrical properties of the solid-state electrolyte, but are further modified to provide more optimized material properties. in this way First, it has a cost advantage in material research and development. Specifically, the present invention utilizes a macromolecule with an epoxy group in its side chain and a siloxane precursor containing a primary amine to prepare a macromolecule with a network structure. Furthermore, polar end groups were introduced by a sol-gel method to prepare a solid electrolyte.

Based on the above basis of the invention, the first object of the present invention is to provide an electrolyte. Specifically, the electrolyte is a solid electrolyte with polar end groups made of cross-linked epoxy/siloxane prepolymer, which includes a salt and a silicon compound; the salt includes lithium salt, sodium salt , potassium salt or a combination thereof, based on the total weight of the electrolyte, the weight percentage of the salt is 10-50 wt %; and the silicon compound has the structure shown in chemical formula (1). Its main application is in the field of battery technology, especially as an electrolyte for lithium batteries to prevent the destruction of lithium dendrites

Specifically, A is a monomer capable of free radical polymerization.

Specifically, L is O, NH or S.

Specifically, R1, R2, R3 and R5 are C1-C4 alkyl, phenyl, benzyl or hydrogen, respectively.

Specifically, R4 is a C1-C8 alkyl group.

Specifically, R6 is a siloxane formed by a -O-Si≡ bond.

Specifically, FG is a functional group having an electron withdrawing group.

Specifically, x is an integer of 1~40, y is 0 (Homopolymer) or an integer of 1~40; and m is an integer of 1~20.

The electrolyte provided by the present invention is an electrolyte with a slightly cross-linked structure. When the electrolyte of the present invention is used as an electrolyte film material of a battery, the electrolyte film material can be prevented from being damaged by metal dendrites, especially lithium dendrites, generated during charging and discharging.

Accordingly, the present invention also provides a method for preventing the battery structure from being damaged by metal dendrites, which comprises using the above-mentioned electrolyte as the solid electrolyte of the battery, so that the metal dendrites (dendrite) generated during the charging and discharging process of the battery are Growth is inhibited or blocked, thereby preventing the cell structure from being damaged by metal dendrites.

The second object of the present invention is to provide a method for synthesizing the silicon compound represented by the chemical formula (1), which comprises the following steps.

Step (1): Provide an organic-inorganic mixture, and the organic-inorganic mixture has the structure shown in the chemical formula (2).

Specifically, A is a monomer that can undergo radical polymerization, and the monomer that can undergo radical polymerization includes poly(ethylene glycol) methyl ether acrylate, methacrylate, methacrylic acid, 2- [[(Butylamino)carbonyl]oxo]ethyl acrylate (2-[[(Butylamino)carbonyl]oxy]ethyl acrylate), Ethyl vinyl ether, or 2-hydroxyethyl methacrylate (2-Hydroxyethyl methacrylate).

Specifically, L is O, NH or S.

Specifically, R1, R2, R3 and R5 are C1-C4 alkyl, phenyl, benzyl or hydrogen, respectively.

Specifically, R4 is a C1-C8 alkyl group.

Specifically, x is an integer of 1~40, y is 0 (Homopolymer) or an integer of 1~40, and m is an integer of 1~20.

Step (2): react the organic-inorganic compound with a siloxane compound having an electron-withdrawing group (FG), thereby obtaining a silicon compound represented by the chemical formula (1), wherein the electron-withdrawing group is The siloxane compound of (FG) is a hydrolyzate of a silicon compound (FG-Si(OR ₇ ) _{3 ), wherein R 7} is a C1-C4 alkyl group.

The present invention also provides a method for blocking the growth of metal dendrites, which comprises using the silicon compound represented by the chemical formula (1) as a barrier for the metal dendrites, thereby blocking the growth of the metal dendrites.

To sum up, the present invention provides an electrolyte with a novel composition, which has the following technical features and unexpected effects: (1) The electrolyte of the present invention is an electrolyte with a slightly cross-linked structure; Electrolytes with slightly cross-linked structures are solid electrolytes with polar end groups made of cross-linked epoxy/siloxane prepolymers. (2) When the electrolyte provided by the present invention is used as the electrolyte film material of the battery, the electrolyte film can be prevented from being damaged by the metal dendrites generated during the charging and discharging process, thereby improving the use safety of the battery and prolonging the battery life. life, so it can be widely used in the battery industry. (3) The silicon compound disclosed in the present invention can also act as a barrier for metal dendrites, thereby preventing the growth of the metal dendrites.

[ Fig. 1 ] is a synthesis route diagram of the solid electrolyte of the present invention.

[ Fig. 2 ] is a hydrogen nuclear magnetic resonance spectrum chart of the polymer copolymer (PG-Epoxy) of the present invention.

[Fig. 3] is a DSC spectrum obtained from a thermal differential analysis experiment.

[Fig. 4] is the result of constant current charge/discharge test of lithium battery with PEO electrolyte in the experimental control group.

[Fig. 5] is a graph showing the test results of constant current charge/discharge of a lithium battery with a solid electrolyte (PGSN-SiCN) having a polar end group (-CN) of the present invention.

[Fig. 6] is a graph showing the test results of the present invention and the solid electrolyte (PGSN-SiCF3) of the present invention and a solid electrolyte (PGSN-SiCF3) with a polar end group (-CF3) at constant current charge/discharge.

According to the above-mentioned purpose of the present invention, the technical features and effects of the present invention are described below with examples and experimental examples.

The first embodiment of the present invention is to provide an electrolyte. Specifically, the electrolyte is a solid electrolyte with polar end groups made of cross-linked epoxy/siloxane prepolymer, which includes a salt and a silicon compound; the salt includes lithium salt, sodium salt , potassium salt or a combination thereof, based on the total weight of the electrolyte, the weight percentage of the salt is 10-50 wt %; and the silicon compound has the structure shown in chemical formula (1).

Specifically, A is a monomer capable of free radical polymerization.

Specifically, L is O, NH or S.

Specifically, R1, R2, R3 and R5 are C1-C4 alkyl, phenyl, benzyl or hydrogen, respectively.

Specifically, R4 is a C1-C8 alkyl group.

Specifically, R6 is a siloxane formed by a -O-Si≡ bond.

Specifically, FG is a functional group having an electron withdrawing group.

Specifically, x is an integer from 1 to 40, and y is 0 (Homopolymer) or an integer from 1 to 40. number; and m is an integer from 1 to 20.

The electrolyte provided by the present invention is an electrolyte with a slightly cross-linked structure. When the electrolyte of the present invention is used as an electrolyte film material of a battery, the electrolyte film material can be prevented from being damaged by metal dendrites, especially lithium dendrites, generated during charging and discharging.

In a preferred embodiment, the lithium salt includes lithium bis(trifluoromethylsulfonyl)amide (LiTFSI), lithium bisfluorosulfonimide (LiFSI), lithium bisoxalatoborate (LiBOB), perchloric acid Lithium (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), or a combination thereof.

In a preferred embodiment, the monomers capable of radical polymerization include poly(ethylene glycol) methyl ether acrylate, methacrylate, methacrylic acid, 2-[[(butylamino)carbonyl] 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate, Ethyl vinyl ether or 2-Hydroxyethyl methacrylate.

In a preferred embodiment, the functional group with electron withdrawing group includes cyanoalkyl, cyanophenyl, fluorophenyl, trifluoromethylphenyl, perfluoroalkylphenyl (perfluoroalkyl)phenyl, trifluoroalkyl or perfluoroalkyl.

In a representative embodiment, the functional group having an electron withdrawing group is cyanopropyl, trifluoropropyl or perfluorooctyl.

In a preferred embodiment, the thermal differential scanning spectrum (DSC) of the electrolyte disclosed in the present invention does not have characteristic peaks of melting point and recrystallization point.

In a representative embodiment, the synthesis reaction route of the electrolyte of the present invention is shown in FIG. 1 . Show. Firstly, poly(ethylene glycol) methyl ether acrylate was mixed with glycidyl methacrylate, and azobisisobutyronitrile (AIBN) was used as an initiator to form a high Molecular copolymer (PG-Epoxy); the polymer copolymer (PG-Epoxy) and 3-aminopropyl triethoxysilane (APTES) are added and mixed in proportion, and the reaction is carried out at room temperature to form an organic-inorganic mixture ( PGA) and adding different proportions of trifluoropropanetrimethoxysilane, 4-triethoxysilyl butyronitrile or perfluorooctyltriethoxysilane to the above organic-inorganic mixture respectively, and adding a certain proportion of dimethoxysilane After lithium (trifluoromethanesulfonyl)imide, hydrolysis and polycondensation is carried out at room temperature to form the cross-linked epoxy/siloxane prepolymer and the solid electrolyte with polar end groups according to the present invention.

The technical effect of the electrolyte described in the first embodiment of the present invention is to provide a method for preventing the battery structure from being damaged by metal dendrites. When the electrolyte described in the first embodiment is used as the solid electrolyte of the battery, the battery can be The growth of metal dendrites generated during charging and discharging is inhibited or blocked, thereby preventing the battery structure from being damaged by metal dendrites.

The second embodiment of the present invention provides a method for synthesizing a silicon compound represented by the chemical formula (1), which includes the following steps.

Step (1): Provide an organic-inorganic mixture, and the organic-inorganic mixture has the structure shown in the chemical formula (2).

Specifically, A is a monomer that can undergo radical polymerization, and the monomer that can undergo radical polymerization includes poly(ethylene glycol) methyl ether acrylate, methacrylate, methacrylic acid, 2- [[(Butylamino)carbonyl]oxo]ethyl acrylate (2-[[(Butylamino)carbonyl]oxy]ethyl acrylate), Ethyl vinyl ether, or 2-hydroxyethyl methacrylate (2-Hydroxyethyl methacrylate).

Specifically, L is O, NH or S.

Specifically, R1, R2, R3 and R5 are C1-C4 alkyl, phenyl, benzyl or hydrogen, respectively.

Specifically, R4 is a C1-C8 alkyl group.

Specifically, x is an integer of 1~40, y is 0 (Homopolymer) or an integer of 1~40, and m is an integer of 1~20.

Step (2): react the organic-inorganic compound with a siloxane compound having an electron-withdrawing group (FG), thereby obtaining a silicon compound represented by the chemical formula (1), wherein the electron-withdrawing group is The siloxane compound of (FG) is a hydrolyzate of a silicon compound (FG-Si(OR ₇ ) _{3 ), wherein R 7} is a C1-C4 alkyl group.

In a preferred embodiment, the electron withdrawing group (FG) comprises cyanoalkyl, cyano Phenyl, fluorophenyl, trifluoromethylphenyl, perfluoroalkylphenyl, trifluoroalkyl or perfluoroalkyl.

In a representative embodiment, the siloxane compound having an electron withdrawing group is a hydrolyzate of the following silicon compounds: trifluoropropane trimethoxysilane, 4-triethoxysilyl butyronitrile, or perfluorooctyl trisulfoxide. Ethoxysilane.

According to the silicon compound represented by the chemical formula (1) synthesized according to the second embodiment of the present invention, the silicon compound represented by the chemical formula (1) acts as a barrier for a metal dendrite, thereby blocking the metal dendrite from grow.

In a representative experimental example, the synthesis route of the solid electrolyte of the present invention is shown in FIG. 1 , and the general steps of the synthesis are as follows.

Add and mix poly(ethylene glycol) methyl ether acrylate and glycidyl methacrylate according to the ratio range disclosed in Table 1, and use azobisisobutyronitrile (AIBN) as an initiator at 70°C. The polymer copolymer (PG-Epoxy) is formed by free radical polymerization; the polymer copolymer (PG-Epoxy) and 3-aminopropyl triethoxysilane are added and mixed according to the proportion, and the reaction is carried out at room temperature to form Organic-inorganic mixture (PGA) and adding different proportions of trifluoropropanetrimethoxysilane, 4-triethoxysilyl butyronitrile or perfluorooctyltriethoxysilane to the above organic-inorganic mixture, respectively, After adding a certain proportion of lithium bis(trifluoromethanesulfonyl)imide, the hydrolysis polycondensation reaction is carried out at room temperature to form the polar cross-linked epoxy/siloxane prepolymer according to the present invention. Terminated solid electrolyte. The product code of the solid electrolyte made of trifluoropropane trimethoxysilane is PGSN-SiCF3. The product code of the solid electrolyte made of 4-triethoxysilyl butyronitrile is PGSN-SiCN. Solids made with perfluorooctyltriethoxysilane The product code of the state electrolyte is PGSN-SiPerF.

Table I

^{The hydrogen nuclear magnetic resonance spectrum ( 1} H-NMR) of the above-mentioned polymer copolymer (PG-Epoxy) is shown in FIG. 2 .

In another experimental example, firstly, a polymer copolymer with epoxy group (PG-Epoxy) was prepared. The monomeric glycidyl methacrylate (GMA) (2 g, 14.06 mmol), the monomeric poly(ethylene glycol) methacrylate (PEGMA; M _n =500) (7.0 g, 14.06 mmol), the initiator AIBN (28.8 mg) and benzoyl The ether anisole (40ml) mixture was subjected to radical polymerization at 70°C for 24 hours, then cooled back to room temperature, and the anisole was removed to obtain a viscous liquid, which was washed with n-hexane and dried in vacuum to obtain a transparent liquid (8g, yield 88%).

A mixture of 2 g (0.20 mol) of 3-aminopropyltriethoxysilane (APTES), 1 g (0.41 mol) of methanol and 0.3 g of water was stirred at room temperature for 30 minutes, then heated to 70°C and stirred for another 30 minutes, A hydrolyzate (ASP) of 3-aminopropyltriethoxysilane is obtained.

Contains 30wt% of epoxy-group copolymer anisole solution (1g, 30wt% of PG in anisole), bis(trifluoromethanesulfonyl) lithium imide (LiTFSI 0.3g), succinonitrile (SN) 0.3 g) and APTES hydrolyzate (0.05 g) were stirred at 60° C. for 30 minutes to thereby obtain an electrolyte precursor solution (PGSN).

4-Triethoxysilylbutyronitrile (1g) was dissolved in ethanol (1ml), then 0.1M HCl (50mg) was added, and stirred at room temperature for 1 hour to obtain a siloxane precursor with polar terminal group (-CN) material (SiCN). Using trifluoropropane trimethoxysilane and perfluorooctyltriethoxysilane respectively in the above manner can obtain a siloxane precursor (SiCF3) with a polar end group (-CF3) and a siloxane precursor with a polar end group (-CF3), respectively. CPerF) siloxane precursor (SiCPerF).

The above-mentioned siloxane precursor (SiCN, 0.05g) with polar terminal group (-CN) was added to the above-mentioned electrolyte precursor solution (PGSN, 1g), stirred at room temperature for 1 hour, and then put into 60 ℃ The oven was heated overnight to remove air bubbles and solvent, and then dried at 60° C. to obtain a yellow solid, that is, the solid electrolyte (PGSN-SiCN) with polar end groups (-CN) of the present invention. Using the siloxane precursor (SiCF3) with a polar end group (-CF3) and the siloxane precursor (SiCPerF) with a polar end group (-CPerF) in the above manner, the polar The solid electrolyte with terminal group (-CF3) (PGSN-SiCF3) and the solid electrolyte with polar terminal group (-CPerF) of the present invention (PGSN-SiCPerF).

The solid electrolyte with polar end group (-CN) (PGSN-SiCN), the solid electrolyte with polar end group (-CF3) (PGSN-SiCF3) and the conventional solid electrolyte PEO of the present invention were thermally tested by a thermal differential scanner. analyze. The DSC spectrum is shown in Figure 3. Obviously, the solid electrolyte of the present invention has no characteristic peaks of melting point and recrystallization point, so the damage to the material structure due to thermal stress caused by phase change can be reduced.

battery performance test

In the control group of the experiment, the electrolyte of PEO/LiTFSI was used as the performance comparison. The electrolyte preparation step was to dissolve polyethylene oxide (PEO, 0.08g) in 1ml of acetonitrile, and add 0.08g of lithium salt. (LiTFSI). After the lithium salt is completely dissolved, the PEO/LiTFSI electrolyte film can be obtained after drying. The PEO/LiTFSI electrolyte film was cut into a 18mm diameter film with a cutter to prepare a CR2032 battery. It can be seen from Figure 4 that the mechanical properties of the PEO/LiTFSI electrolyte film are not good, and the phenomenon of short circuit and overcharge caused by lithium dendrites during the charging process.

A test cell (type: CR2032) was sequentially equipped with a LiFePO ₄ anode, a solid electrolyte with polar end groups of the present invention, and a cathode (Li). The charge-discharge cycle test instruments are blue-electric charge-discharger (CT3001A) and electrochemical analyzer (CH Instruments CHI-614D). The test voltage was 2.5 to 4.2 volts (V) and the temperature was 80°C. The test charts of the lithium battery constant current charge and discharge experiments of the solid electrolyte (PGSN-SiCN) with polar end groups (-CN) or the solid electrolyte (PGSN-SiCF3) with polar end groups (-CF3) of the present invention are shown in Figure 5 and shown in Figure 6. Obviously, none of the test results showed that the battery was short-circuited and overcharged. Accordingly, it is proved that the solid electrolyte of the present invention can effectively prevent the damage of lithium dendrites to the battery structure. Therefore, the lithium battery made by using the solid electrolyte of the present invention has the advantages of no short-circuit overcharge due to the growth of lithium dendrites during the charging process. technical effect.

Although the present invention is described above with specific experimental examples, it does not limit the scope of the present invention. As long as it does not depart from the gist of the present invention, those skilled in the art will understand that various modifications or changes can be made without departing from the intent and scope of the present invention. In addition, the abstract section and the title are only used to aid the search of patent documents and are not intended to limit the scope of the present invention.

Claims (11)

An electrolyte, the electrolyte comprises a salt and a silicon compound; the salt comprises a lithium salt, a sodium salt, a potassium salt or a combination thereof, and based on the total weight of the electrolyte, the weight percentage of the salt is 10-50wt %; and the silicon compound has the structure shown in chemical formula (1):

Wherein, A is a monomer that can carry out radical polymerization reaction; L is O, NH or S; R1, R2, R3 and R5 are C1~C4 alkyl, phenyl, benzyl or hydrogen respectively; R4 is C1~C8 alkyl group; R6 is a siloxane (siloxane) formed by -O-Si≡ bond; FG is a functional group with electron withdrawing group; and x is an integer of 1~40, y is 0 (Homopolymer) or an integer from 1 to 40; and m is an integer from 1 to 20. The electrolyte of claim 1, wherein the lithium salt comprises lithium bis(trifluoromethylsulfonyl)amide (LiTFSI), lithium bisfluorosulfonimide (LiFSI), lithium bisoxalatoborate (LiBOB), perchloric acid Lithium (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), or a combination thereof. According to the electrolyte of claim 1, the monomer capable of radical polymerization comprises poly(ethylene glycol) methyl ether acrylate, methacrylate, methacrylic acid, 2-[[(butylamino)carbonyl] 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate, Ethyl vinyl ether or 2-Hydroxyethyl methacrylate. According to the electrolyte of claim 1, the functional group with electron withdrawing group comprises cyanoalkyl, cyanophenyl, fluorophenyl, trifluoromethylphenyl, perfluoroalkylphenyl (perfluoroalkyl)phenyl, trifluoroalkyl or perfluoroalkyl. According to the electrolyte of claim 1, the functional group with electron withdrawing group is cyanopropyl group, trifluoropropyl group or perfluorooctyl group. According to the electrolyte of claim 1, its DSC spectrum has no characteristic peaks of melting point and recrystallization point. A method for preventing a battery structure from being damaged by metal dendrites, comprising using the electrolyte as described in claims 1 to 6 as a solid electrolyte of the battery, so that the battery grows metal dendrites (dendrite) generated during charging and discharging is inhibited or blocked, thereby preventing the cell structure from being damaged by metal dendrites. A method for synthesizing a silicon compound represented by chemical formula (1) as described in the electrolyte of claim 1, comprising: (1) providing an organic-inorganic mixture, the organic-inorganic mixture having a structure as shown in chemical formula (2) :

Wherein, A is a monomer capable of radical polymerization, and the monomer capable of radical polymerization includes poly(ethylene glycol) methyl ether acrylate, methacrylate, methacrylic acid, 2-[ [(Butylamino)carbonyl]oxo]ethyl acrylate (2-[[(Butylamino)carbonyl]oxy]ethyl acrylate), Ethyl vinyl ether or 2-hydroxyethyl methacrylate ( 2-Hydroxyethyl methacrylate); L is O, NH or S; R1, R2, R3 and R5 are respectively C1~C4 alkyl, phenyl, benzyl or hydrogen; R4 is C1~C8 alkyl; x is an integer of 1 to 40, y is an integer of 0 (Homopolymer) or an integer of 1 to 40, and m is an integer of 1 to 20; and (2) making the organic-inorganic compound and a silicon having an electron withdrawing group (FG) The oxane compound is reacted to obtain a silicon compound shown in chemical formula (1), wherein the siloxane compound having an electron withdrawing group (FG) is the hydrolysis _{of the silicon compound (FG-Si(OR 7} ) _{3 )} compound, wherein R ₇ is a C1-C4 alkyl group. The method for synthesizing the silicon compound represented by the chemical formula (1) according to the electrolyte of claim 1 according to claim 8, wherein the electron withdrawing group comprises a cyanoalkyl group, a cyanophenyl group, and a fluorophenyl group. , trifluoromethylphenyl (trifluoromethyl)phenyl, perfluoroalkylphenyl (perfluoroalkyl)phenyl, trifluoroalkyl (trifluoroalkyl) or perfluoroalkyl (perfluoroalkyl). The method for synthesizing the silicon compound represented by the chemical formula (1) according to the electrolyte of claim 1 according to claim 8, wherein the siloxane compound having an electron-withdrawing group is a hydrolyzate of the following silicon compound: three Fluoropropane trimethoxysilane, 4-triethoxysilylbutyronitrile or perfluorooctyltriethoxysilane. A method for blocking the growth of metal dendrites, comprising using a silicon compound represented by chemical formula (1) as described in the electrolyte of claim 1 as a barrier for the metal dendrites, thereby blocking growth of the metal dendrites.

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